BIO 425 Exam II Study Guide: Antigens, Antibodies, Cytokines, and Complement

Vocabulary practice flashcards covering antigens, antibody structure and classes, cytokine signaling pathways, and complement system components from the BIO 425 Exam II study guide.

Antigen

A foreign substance or molecule capable of binding specifically to an antibody or immune cell receptor to elicit an immune response.

Epitope

The specific region, surface feature, or antigenic determinant on an antigen that is recognized and bound by an antibody or receptor.

Paratope

The antigen-binding site of an antibody molecule that specifically recognizes and interacts with an epitope.

Hapten

A low-molecular-weight molecule that can bind to an antibody but cannot elicit an immune response on its own unless conjugated to a larger carrier molecule.

Antibody

An immunoglobulin glycoprotein secreted by plasma cells that binds specifically to an antigen to target it for elimination.

Monoclonal Antibodies

Identical antibodies produced by a single clone of hybridoma or B cells that bind with uniform affinity to a single specific epitope.

Polyclonal Antibodies

A heterogeneous mixture of antibodies secreted by multiple distinct B cell clones that recognize multiple epitopes on the same antigen.

Antibody Effector Functions

The biological mechanisms by which antibodies facilitate pathogen elimination, including neutralization, opsonization, complement activation, and antibody-dependent cellular cytotoxicity.

Cytokines

Low-molecular-weight soluble regulatory proteins secreted by immune and other cells that mediate cell-to-cell communication in innate and adaptive immunity.

Interleukin-33 (IL-33)

An alarm-signaling cytokine belonging to the IL-1 family that functions in host defense and mucosal immune regulation.

Interleukin-18 (IL-18)

A pro-inflammatory cytokine belonging to the IL-1 family that promotes interferon-gamma production and stimulates cell-mediated immune responses.

Interleukin-2 (IL-2) Receptor Family

A group of multimeric cytokine receptors characterized by shared receptor subunits (such as the common gamma chain) that mediate lymphocyte proliferation and survival.

JAK-STAT Pathway

A cytokine signal transduction pathway named after Janus kinases (JAK) and Signal Transducer and Activator of Transcription (STAT) proteins that transmits signals directly from cell-surface receptors to the nucleus.

TNF-Fas Receptor Signaling

Signaling cascades triggered by TNF and Fas family receptors that regulate inflammatory responses, cell survival, or extrinsic apoptotic death pathways.

Complement

A biochemical cascade of plasma and membrane-bound proteins, designated $C1$ through $C9$ and regulatory factors, that enhances pathogen opsonization, lysis, and inflammation.

Classical Pathway

A complement activation pathway typically initiated by the binding of antibodies (such as IgG or IgM) within an immune complex to the $C1$ macromolecular complex.

Alternative Pathway

An antibody-independent complement activation pathway triggered directly by the spontaneous hydrolysis of $C3$ and interaction with foreign microbial surfaces.

$C1$ Macromolecular Complex

A multi-subunit initiator complex of the classical pathway composed of $C1q$, $C1r$, and $C1s$ that binds to the Fc regions of antigen-bound antibodies.

Complement Deficiency

A state of absent or dysfunctional complement proteins that leads to clinical consequences such as recurrent bacterial infections or autoimmune disorders.